Weight classes* at four ages, The Tromsø Study, Fit Futures observed cases†
| Age | 2–4 years | 5–7 years | 15–17 years | 18–20 years | |||||
| n | % | n | % | n | % | n | % | ||
| Girls | Underweight | 48 | 14.6 | 37 | 10.5 | 24 | 5.1 | 16 | 4.4 |
| Normal weight | 234 | 71.3 | 250 | 71.0 | 347 | 74.3 | 271 | 74.7 | |
| Overweight | 41 | 12.5 | 49 | 13.9 | 70 | 15.0 | 52 | 14.3 | |
| Obesity | 5 | 1.5 | 16 | 4.6 | 26 | 5.6 | 24 | 6.6 | |
| Total | 328 | 100.0 | 352 | 100.0 | 467 | 100.0 | 363 | 100.0 | |
| Boys | Underweight | 43 | 12.3 | 28 | 7.3 | 38 | 7.7 | 24 | 8.1 |
| Normal weight | 276 | 78.9 | 314 | 81.8 | 339 | 68.9 | 189 | 63.9 | |
| Overweight | 27 | 7.7 | 27 | 7.0 | 79 | 16.1 | 59 | 19.9 | |
| Obesity | 4 | 1.1 | 15 | 3.9 | 36 | 7.3 | 24 | 8.1 | |
| Total | 350 | 100.0 | 384 | 100.0 | 492 | 100.0 | 296 | 100.0 | |
*Weight classes according to the International Obesity Taskforce (IOTF) age- and sex-specific cut-off values for children 2–18 years of age and the WHO index for adults from age 18–20.21 22
†In observed cases n is varying at different ages from 659 to 959.